The invention is based on a heating system as generically defined by the preamble to claim 1.
In some operating states of an internal combustion engine, such as cold starting, short trips, or long downhill trips by motor vehicles, the heat input into the coolant from the engine itself is no longer sufficient, especially if the efficiency of the engine is very high, as in the case of direct gasoline injection, high pressure diesel injection with a common rail, or a highly charged engine with a turbocharger, since then only slight heat losses occur. Accordingly, the engine and its catalytic converter do not reach their optimal temperatures within the brief available time, or do so only quite late, which leads to increased fuel consumption and increased exhaust emissions.
Since at low outdoor temperatures considerable amounts of heat are required to de-ice the vehicle windows or to heat the passenger compartment, both driving safety and comfort are restricted. Furthermore, future drive system concepts, such as hybrid vehicles, require an additional heat source during electrical operation in order to heat the passenger compartment or the catalytic converter. This problem is currently solved predominantly by using chemical or electrical auxiliary heaters. Chemical auxiliary heaters, such as burners, do offer great comfort because of the capability of heating even while the engine is at a stop, but are relatively expensive. Conventional electrical auxiliary heaters operating on the principle of resistance heating are highly limited in power, because the generator cannot make enough current available.
According to the invention, a combustion chamber is connected to the exhaust system of the internal combustion engine in the region of an exhaust manifold of the internal combustion engine, between outlet valves and a exhaust gas catalytic converter, via an exhaust line. As needed, the combustion chamber is put into operation, so that by it, hot exhaust gases of the exhaust system of the engine are heated. This includes primarily the exhaust gas catalytic converter, which very quickly reaches its optimal operating temperature, but also the exhaust conduits as far as the outlet valves, and as a result, the engine itself and especially its cylinder head reaches its operating temperature faster.
To achieve a more-intensive heat exchange between the combustion chamber and the engine, it is expedient that coolant conduits of a heat exchanger surround the combustion chamber and are connected to a coolant system of the engine. Thus the combustion chamber can on the one hand already preheat the engine before the engine is started, and on the other, the heater connected to the coolant system of the engine can take care of the passenger compartment. Via electronically triggered valves, the quantity of heat can be distributed to suit existing priorities.
In supercharged engines, the combustion chamber can also serve to improve the response performance of the exhaust gas turbocharger, by increasing the quantity and energy of the exhaust gas in the lower rpm range. The resultant higher rpm of the exhaust gas turbine and the radial compressor makes a higher charge pressure possible, which leads to improved acceleration of the engine at more favorable efficiency. The exhaust gas turbine is expediently disposed upstream of the exhaust gas catalytic converter and can be circumvented by a bypass that has a control device. As a result, the exhaust gas turbine can be regulated. Furthermore, because of the bypass, hot exhaust gases while the engine is at a stop reach the catalytic converter directly and already bring it to a suitable operating temperature before the engine is started.
By means of the heating system of the invention, it is thus possible to meet all the demands made of a modern internal combustion engine with only a single combustion chamber and at little engineering effort and expense.